I recently received a 3 pce nailer set as a Christmas gift and has been absolutely wonderful except for some reason the brad nailer unit seems to have lost it's seal today and will no longer work. The air continually exhausts now through the cap exhaust hole and I don't know how to stop it. I've disassembled everything and have inspected the gaskets but everything seems fine. The troubleshooting info in the manual doesn't list this specific problem so I don't know what to do and I don't have the receipt as it was a gift. Hoping someone can help. Please advise.